What attracted Stevenson to Fanny as noted in the nonfiction book, Across America on an Emigrant Train?

According to Murphy: As far as he [Stevenson] was concerned, Fanny was perfect in every way. She was small and fine-boned, with a dark, mysterious complexion. An acquaintance of Stevenson's noted that her "eyes were full of . .. mystery as they changed from fire to fun to gloom or tenderness." Stevenson wasn't attracted to her simply because of her exotic looks. He admired her independent spirit, her keen mind, and her strong opinions. She could talk intelligently and with authority on a wide number of sub jects, from art and politics to travel and literature.